/*
 * Copyright � 2002-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System.Collections.Specialized;

namespace Spring.Objects.Factory.Config;

/// <summary>
/// Tag class which represent a Spring-managed <see cref="NameValueCollection"/> instance that
/// supports merging of parent/child definitions.
/// </summary>
public class ManagedNameValueCollection : NameValueCollection, IMergable
{
    private bool mergeEnabled;

    /// <summary>
    /// Initializes a new instance of the <see cref="T:System.Collections.Specialized.NameValueCollection"/> class that is empty, has the default initial capacity and uses the default case-insensitive hash code provider and the default case-insensitive comparer.
    /// </summary>
    public ManagedNameValueCollection()
    {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="T:System.Collections.Specialized.NameValueCollection"/> class that is empty, has the specified initial capacity and uses the default case-insensitive hash code provider and the default case-insensitive comparer.
    /// </summary>
    /// <param name="capacity">The initial number of entries that the <see cref="T:System.Collections.Specialized.NameValueCollection"/> can contain.</param><exception cref="T:System.ArgumentOutOfRangeException"><paramref name="capacity"/> is less than zero.</exception>
    public ManagedNameValueCollection(int capacity) : base(capacity)
    {
    }

    /// <summary>
    /// Gets a value indicating whether this instance is merge enabled for this instance
    /// </summary>
    /// <value>
    /// 	<c>true</c> if this instance is merge enabled; otherwise, <c>false</c>.
    /// </value>
    public bool MergeEnabled
    {
        get { return this.mergeEnabled; }
        set { this.mergeEnabled = value; }
    }

    /// <summary>
    /// Merges the current value set with that of the supplied object.
    /// </summary>
    /// <remarks>The supplied object is considered the parent, and values in the
    /// callee's value set must override those of the supplied object.
    /// </remarks>
    /// <param name="parent">The parent object to merge with</param>
    /// <returns>The result of the merge operation</returns>
    /// <exception cref="ArgumentNullException">If the supplied parent is <code>null</code></exception>
    /// <exception cref="InvalidOperationException">If merging is not enabled for this instance,
    /// (i.e. <code>MergeEnabled</code> equals <code>false</code>.</exception>
    public object Merge(object parent)
    {
        if (!this.mergeEnabled)
        {
            throw new InvalidOperationException(
                "Not allowed to merge when the 'MergeEnabled' property is set to 'false'");
        }

        if (parent == null)
        {
            return this;
        }

        NameValueCollection pDict = parent as NameValueCollection;
        if (pDict == null)
        {
            throw new InvalidOperationException("Cannot merge with object of type [" + parent.GetType() + "]");
        }

        NameValueCollection merged = new ManagedNameValueCollection();
        foreach (string s in pDict.AllKeys)
        {
            merged[s] = pDict.Get(s);
        }

        foreach (string s in this.AllKeys)
        {
            merged[s] = this.Get(s);
        }

        return merged;
    }
}
